Legend 1. There is a worm.
Check. Full stop.
Legend 2. The worm is powerful enough to bring the World to an End.
Check.
Spoiler
Maybe. We never get to see the Worm itself, to see whether the Tree is some kind of antler, or maybe some other protruding element. But there is implication.
Legend 4. The Earth is some kind of secretion from the Worm as it slept.
Does not appear to be the case, though not categorically denied. Seems more like a cyst the universe formed around it to protect itself from an irritant. Much like a Pearl or a plant gall.
Legend 5. It likes to snack on stars, and by extension, Elohim.
Check. Sorta. Since we don't see it cavorting in the sky, I have to assume the legend has it backwards. It is clear that the worm has a sweet tooth for EarthPower in general. Elohim are effectively "Popcorn Earthpower", and so as the Worm finds and eats an Elohim, their corresponding star gets extinguished.
Spoiler
You Betcha!
Spoiler
Plausible. When envisioning the Worm as something that could secrete the rest of the world as a skin, something as small as a Nicor didn't seem reasonable. Now that we know the approximate size of the beast, the scale of Nicor doesn't seem so off.